I've felt that pounding before, only we went from 6 to 2 knots, with a tide going against some very square waves, due to the wind and current fighting ea other! A lot of boats were pounding in those seas from comments from YC members coming home from a cruise. Other than the 40-50' 30K disp powerpoats, they drove thru.
She drives me boat,
I drives me dinghy!